Abstract. The spaceborne passive microwave sensors Soil Moisture Ocean Salinity (SMOS) and Soil Moisture Active Passive (SMAP) provide brightness temperature data at L-band (1.4GHz). At this low frequency the atmosphere is close to transparent and in polar regions the thickness of thin sea ice can be derived. SMOS data covers a large incidence angle range whereas SMAP observes at a fixed 40° incidence angle which makes thin sea ice thickness retrieval more stable as incidence angle effects do not have to be taken into account. Here we transfer a retrieval algorithm for thickness of thin sea ice (up to 50cm) from SMOS data at 40° to 50° incidence angle to the fixed incidence angle of SMAP. Now the SMOS brightness temperatures (TBs) at a given incidence angle are estimated using empirical fit functions. SMAP TBs are calibrated to SMOS for providing a merged SMOS/SMAP Sea Ice Thickness product.

Sea ice thickness is important for representing atmosphere-ocean interactions in climate models. A validated satellite sea ice thickness measurements algorithm is transfered to a new sensor. The results offer a better temporal and spatial coverage of satellite measurements in the polar regions. Here we describe the calibration procedure between the two sensors taking into account their technical differences. In addition a new filter for interferences from artificial radio sources is implemented.

Sea ice thickness is important for representing atmosphere-ocean interactions in climate models....